1. The Field of the Invention
The present invention generally relates to x-ray tubes. More particularly, the present invention relates to a mounting system for an x-ray tube that simplifies the loading and positioning of a tube insert within an outer housing of the tube.
2. The Related Technology
X-ray generating devices are extremely valuable tools that are used in a wide variety of applications, both industrial and medical. For example, such equipment is commonly employed in areas such as medical diagnostic examination and therapeutic radiology, semiconductor manufacture and fabrication, and materials analysis.
Regardless of the applications in which they are employed, x-ray devices operate in similar fashion. In general, x-rays are produced when electrons are emitted, accelerated, and then impinged upon a material of a particular composition. This process typically takes place within an evacuated enclosure of an x-ray tube. Disposed within the evacuated enclosure is a cathode and an anode oriented to receive electrons emitted by the cathode. The anode can be stationary within the tube, or can be in the form of a rotating annular disk that is mounted to a rotor shaft and bearing assembly. The evacuated enclosure is typically contained within an outer housing, which also serves as a coolant reservoir.
In operation, an electric current is supplied to a filament portion of the cathode, which causes a cloud of electrons to be emitted via a process known as thermionic emission. A high voltage potential is placed between the cathode and anode to cause the cloud of electrons to form a stream and accelerate toward a focal spot disposed on a target surface of the anode. Upon striking the target surface, some of the kinetic energy of the electrons is released in the form of electromagnetic radiation of very high frequency, i.e., x-rays. The specific frequency of the x-rays produced depends in large part on the type of material used to form the anode target surface. Target surface materials with high atomic numbers (“Z numbers”) are typically employed. The target surface of the anode is oriented so that at least some of the x-rays are emitted through x-ray transmissive windows defined in the evacuated enclosure and the outer housing. The emitted x-ray signal can then be used for a variety of purposes, including materials analysis and medical evaluation and treatment.
To assemble an x-ray tube as described above, the evacuated enclosure is typically secured within the outer housing using various internal mounting structures. While such structures adequately secure the evacuated enclosure, they nonetheless suffer from various setbacks. Among these is the fact that the use of such structures requires a relatively complex procedure and necessitates the expenditure of a significant amount of time and energy in properly mounting and aligning the evacuated enclosure within the outer housing. Because of the relatively complex procedure that must be followed, positioning of the evacuated enclosure within the outer housing to achieve optimum focal spot positioning of emitted x-rays can be difficult.
Further complicating the above situation is the fact that in many x-ray tubes the outer housing is filled with a dielectric oil that acts as both a conductive barrier and a cooling medium. Such oil-filled outer housings equate to even more time and expense when placing an evacuated enclosure within the housing during tube assembly because of the various fluid seals that must be included between the two components, especially in the x-ray passage region defined between the enclosure window and the window of the outer housing.
In addition, the aforementioned challenges consequently create further problems after initial tube assembly. An x-ray tube, once manufacture and assembly is complete, is typically disposed within an x-ray generating device, such as a CT scanner or mammography imaging apparatus, to produce x-rays needed for use by such devices. For instance, a mammography imaging apparatus produces images that are utilized to detect abnormal masses, such as tumors, in human breast material. An x-ray tube located within the mammography apparatus emits a beam of x-rays that enables such images to be produced. Such x-ray tubes can occasionally require replacement due to various conditions. When replacement is needed, it is frequently preferable to replace only the evacuated enclosure portion of the x-ray tube, as opposed to the entire x-ray tube, including the outer housing. Such on-site change-out of the evacuated enclosure portion of the x-ray tube, though desirable, is nonetheless often precluded because of the difficulties expressed above that are encountered when installing an evacuated enclosure within an outer housing.
In light of the above challenges, a need exists in the art for an improved x-ray tube mounting system. In particular, a mounting system is needed that enables tube components, such as the evacuated enclosure and outer housing, to be assembled and secured to one another in a simplified fashion, thereby saving time and resources otherwise spent during the assembly process. The mounting system should be capable of supporting the evacuated enclosure within the outer housing without the need for additional supporting structures. The mounting system should also readily provide for fixation of the x-ray tube to an x-ray generating device, such as a medical imaging apparatus. Finally, any mounting system should also enable mounting of the evacuated enclosure within the outer housing without regard to whether the outer housing is filled with dielectric oil.